1. Field of the Invention
The present invention relates to a backlight system used in a liquid crystal display (LCD), and particularly to a liquid crystal display and a backlight system used therein having uniform luminance.
2. General Background
In general, LCDs have two main advantages in comparison with cathode ray tubes (CRTs): LCDs are thin, and have low power consumption. It has been said that LCDs might one day completely replace CRT display devices, and LCDs have aroused great interest in many industries in recent times. In general, an LCD needs a surface light source to provide even light for a clear display.
A typical surface light source comprises a light source and a light guide plate. The light source may be a linear light source, or one or more point light sources. The light guide plate has an end face through which light is introduced, and two opposite major faces one of which functions as a light emission face. The performance of the surface light source greatly depends on the characteristics of the light guide plate employed therein.
The light guide plate functions to change a direction of propagation of light beams emitted from the light source and introduced into the light guide plate, from a direction roughly parallel to the emission face of the light guide plate to a direction perpendicular to the emission face. That is, the light guide plate effectively changes the linear or point light source(s) into a surface light source, for evenly illuminating a whole display screen of the LCD. The light guide plate often further comprises a plurality of scattering dots disposed on the bottom surface, for eliminating total internal reflection of light beams in the light guide plate. That is, the scattering dots diffuse the light beams, thereby improving the uniformity of brightness of the light guide plate and enhancing the optical characteristics of the LCD. Different LCDs require scattering dots having different shapes, sizes, and distribution densities depending on the different uses to which the LCDs are put.
FIG. 7 shows a conventional LCD 1, which comprises a top frame 11, an LCD panel 12, a surface light source 13, and a bottom frame 14. The LCD panel 12 and the backlight system 13 are accommodated a the space cooperatively defined by the top frame 11 and the bottom frame 14. The backlight system 13 is disposed under the LCD panel 12 for providing the light beams to the LCD panel 12. The backlight system 13 comprises a light guide plate 133, a reflector 134, a diffuser 135, a brightness enhancement film (BEF) 136, a linear light source 131, and a lamp cover 132 covering three sides of the linear light source 131. The BEF 136, the diffuser 135, the light guide plate 133 and the reflector 134 are stacked one on the other in that order from top to bottom. The linear light source 131 is disposed adjacent to one side of the light guide plate 133.
In assembly of the LCD 1, a relatively complicated working process is required. In addition, if the lamp 131 needs to be exchanged, the reflector 134 and the frames 11, 14 must all be detached. These disadvantages are unduly laborious and time-consuming.
What is needed, therefore, is a simple, compact LCD with a backlight system, which is easy to assemble and which allows easy exchange of a built-in light source.